1. Field of the Invention
The present invention relates to a shelf-stable aseptic dairy product which is capable of forming a stable foam upon whipping and to a process for preparing the same. The dairy product is shelf-stable for up to several months.
2. Background
For many years there has been an interest in the production of shelf-stable dairy products. Fluid dairy products can be preserved for short periods of time by refrigeration, but nonetheless deteriorate fairly rapidly due to microbiological activity. Pasteurization slows down such deterioration somewhat but does not prevent it.
While refrigerated dairy products have the advantage of fresh taste, several disadvantages exist. In addition to the inconvenience to the consumer of having to obtain fresh dairy products on a frequent basis, fresh dairy products incur costs to the distributor which translate into an increased price for the consumer; for example, the products must be distributed and marketed under cooled conditions, and dairy products which have sat on the shelf for more than a few days become unfit for consumption and must be returned to the distributor. Of particular interest, therefore, has been a dairy cream product having a long shelf life, inasmuch as dairy cream is a "Sunday product" which is typically used only on an infrequent basis.
Within the past thirty years, aseptic packaging systems have been developed to provide commercially feasible packaging of sterile dairy products intended for long term storage without refrigeration. These systems make use of ultra-high temperature (UHT) treatment. UHT treatment produces a product that is free of spoilage organisms by heating the fluid dairy product to a temperature that is high enough to kill spore-forming organisms, for a sufficiently short period of time so as to minimize the physical and chemical changes in the product itself. Common process parameters for UHT treatment are a temperature in the range of 140.degree. C. to 150.degree. C. for a time from 2 to 7 seconds. By utilizing the UHT treatment in conjunction with an aseptic filling system, packaged fluid dairy products can be produced that remain fresh at ambient temperature for extended periods. The techniques and equipment that are required for UHT processing and for aseptic filling are well known in the art.
While UHT processing significantly increases shelf life of dairy products, several disadvantages may result from high temperature treatment. For example, UHT-treated dairy products tend to exhibit some flavor defects and fat emulsion instability on standing. It is theorized that this instability, which manifests itself as fat separation among other thins, is most likely caused by a change in the physical relationship between the fat, casein, and denatured serum proteins in the dairy product because of the UHT processing. This problem would be expected to be particularly significant for high fat content dairy products such as whipping cream.
In order to overcome this instability, homogenization is required to obtain a uniform and stable cream emulsion. However, homogenization will reduce the whipping properties of a dairy product intended for use in making whipped cream and syneresis is often seen in the whipped foam during standing, as well as excessive gelation caused by fat clustering, especially if the product is refrigerated before use.
Yet another deficiency is that ultra-high temperature treated dairy creams often have poor whipping properties which cause the whipped foam to be too weak and to have poor stand-up, making it unsuitable for decoration purposes, such as in bakeries and restaurants.
In order to maintain a cream product in an instantly whippable form, monoglyceride emulsifiers have been added to cream products. For example, U.S. Pat. No. 4,375,485 to Van Gennip discloses the use of lactic acid esters of monoglycerides for this purpose. However, this patent requires first separating out butter fat and lactic acid from the cream in order to preserve a desirable taste quality.
It is therefore an object of the present invention to provide a whippable dairy product which has a long shelf life at room temperature.
It is a further object to provide a dairy product which is present as a stable emulsion and which, when whipped, forms a foam which has acceptable foaming properties and a uniform consistency.
It is a still further object of the invention to provide an economical process for preparing a whippable dairy product which has a long shelf life at room temperature, is present as a stable emulsion and which, when whipped, forms a foam which has acceptable foaming properties and a uniform consistency.